973项目信号传导新机制登上权威杂志

生物谷

生物谷综合报道：来自中科院中科院生物物理研究所，武汉大学生科院的研究人员在原有工作基础上，进一步研究TNF家族CD154分子及其受体CD40调控内皮细胞炎症反应的信号传导机制。该研究成果公布在心血管研究权威杂志Arteriosclerosis, Thrombosis, and Vascular Biology上，通讯作者为生物物理所唐宏博士，此项研究受到科技部973研究计划资助。这一研究为解释动脉粥样硬化形成过程中内皮细胞炎症反应的信号机制提供了依据，也为他汀类(statin)降胆固醇药物治疗动脉粥样硬化提供了新的研究思路。

脂筏是受体传递信号的重要载体。大多数TNF受体通过网格蛋白(clathrin)-胆固醇复合体内吞而传递信号。CD40的不同活性形式配体(可溶性和细胞膜性)决定了受体通过膜窖内吞或者脂筏聚集激活内皮细胞的炎症反应的发现将丰富人们对动脉内皮细胞炎症反应在动脉粥样硬化症致病机理的认识，同时为相关疾病的诊治提供新的理论依据。

在这篇文章中，研究人员发现细胞胆固醇水平决定了可溶性CD154通过胞膜窖(caveolae)脂筏激活CD40的内吞(endocytosis)与信号转导，而细胞膜上表达CD154则形成不依赖于胆固醇的脂筏聚集从细胞膜表面传递信号。该研究结果为解释动脉粥样硬化形成过程中内皮细胞炎症反应的信号机制提供了依据，也为他汀类(statin)降胆固醇药物治疗动脉粥样硬化提供了新的研究思路。

原始出处：
Published online before print July 12, 2007
(Arteriosclerosis, Thrombosis, and Vascular Biology 2007, doi:10.1161/ATVBAHA.107.145961)

Submitted on April 13, 2007
Accepted on June 22, 2007

Cholesterol-Dependent and -Independent CD40 Internalization and Signaling Activation in Cardiovascular Endothelial Cells

Jianjun Chen ; Lu Chen ; Gang Wang ; and Hong Tang *

From the Institute of Microbiology (J.C.), Institute of Biophysics (G.W., H.T.), Chinese Academy of Sciences, Beijing, and Wuhan University College of Life Sciences (L.C.), Wuhan, China.

* To whom correspondence should be addressed. E-mail: tanghong@moon.ibp.ac.cn .

Objective--It remains elusive how CD40 endocytosis or clustering on the cell surface is induced by different forms of CD40 agonist. This study aims to investigate whether lipid rafts differentially regulate CD40 traffic and signaling in proinflammatory activation of cardiovascular endothelial cells (ECs).

Methods and Results--Using fluorescent microscopy and flow cytometry, we demonstrated that soluble CD40L and agonistic antibody G28.5 induced CD40 internalization via clathrin-independent pathway. Furthermore, depletion of cholesterol by methyl- ${beta}$ -cyclodextrin (MCD) or siRNA knockdown of caveolin-1 efficiently blocked CD40 internalization, suggesting that caveolae-rafts pathway regulates CD40 internalization. In contrast, a membrane-bound CD40L mimic (megamer) triggered aggregation of CD40 rafts outside of the conventional cholera toxin B subunit-positive lipid rafts resistant to cholesterol depletion. Finally, both G28.5 and megamer induced CD40 translocation to Brij58-insoluble, low buoyant density rafts, a movement insensitive to cholesterol depletion. However, MCD effectively inhibited G28.5 but not megamer-induced CD40 activation, and such inhibition could be alleviated by cholesterol reconstitution, suggesting that 2 different raft structures of CD40 induced by G28.5 or megamer possess differential sensitivity to cellular cholesterol levels in downstream signaling.